New pretreatment method for immunohistochemistry for abnormal prion protein

Abstract

Immunohistochemistry for prion protein (PrP) is essential for pathological diagnosis of prion diseases, however, certain pretreatment procedures are required for antigen retrieval of formalin-fixed paraffin-embedded sections. Although hydrolytic autoclaving and formic-acid treatment are usually employed, these methods tend to result in nonspecific high background staining and poorly preserved sections. Thus, we tried autoclaving of the sections with nonionic detergent as follows: autoclave sections with 0.1% Triton X-100 in 50mM Tris-HCI buffer pH7.6, 121°C 20 minutes. Both monoclonal antibody (clone 3F4) and polyclonal anti-PrP-C-terminal antibody were used for human cases with Creutzfeldt-Jakob disease and mouse models of transmissible spongiform encephalopathies. This detergent autoclaving method resulted in significantly higher signal/noise ratio for accumulated PrP in the follicular dendritic cells compared to conventional pretreatment methods. Although synaptic staining in the brain was obtained rather weakly than with conventional methods, pretreatment with detergent autoclaving contributed to lower background and well preserved sections so that we could recognize PrP deposition well. Normal-form cellular PrP was not immunostained in control cases. These results were observed for both monoclonal and polyclonal antibodies, and both human and murine materials. The lower background staining, obtained with detergent autoclaving, enabled double immunofluorescence efficiently on the same sections. We, thus, propose the detergent autoclaving method as a useful choice of the pretreatment for PrP immunohistochemistry